JP3743530B2 - Gas turbine combustor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustor for a gas turbine that reduces the concentration of nitrogen oxides (NO _x ) in exhaust gas.
[0002]
[Prior art]
As illustrated in FIG. 5, the gas turbine is composed of an air compressor, a combustor, a turbine, and the like, and fuel is combusted in the combustor by the air pressurized by the air compressor to generate high-temperature combustion gas. The turbine is driven by this high-temperature combustion gas, and the air compressor is driven to rotate by the turbine. Further, in the gas turbine illustrated in FIG. 5, a large number of combustors are arranged around. However, in the gas turbine for onshore or aircraft auxiliary power, from the viewpoint of exhaust gas countermeasures, improvement in maintainability, cost, etc. Many have only a single combustor.
[0003]
In recent years, nitrogen oxide (NO _x ) generated at the time of combustion has become a major problem due to environmental considerations. NO _x discharged from the combustor that uses less fuel with (e.g. natural gas) nitrogen component is a so-called thermal NO _x nitrogen in the air is oxidized in the high temperature region. In the diffusion combustion normally used in the conventional gas turbine combustor, the adiabatic flame temperature reaches about 2000 ° C., which causes a problem that a large amount of thermal NO _x is generated due to this high temperature. On the other hand, the thermal NO _x is known can be reduced by lowering the flame temperature, the premixed combustion is adopted in place of a conventional diffusion combustion, fuel and combustion air is premixed lean mixture of fuel Attempts have already been made to suppress the generation of NO _x by using gas as a gas and burning it at a relatively low temperature.
[0004]
[Problems to be solved by the invention]
However, in (1) premixed combustion, if the fuel gas becomes lean, the combustion stability range becomes narrow, and there is a problem that reliable ignition and stable combustion become difficult. In order to solve this problem, in Japanese Patent Laid-Open No. 63-217141, ignition and combustion are stably performed by diffusion combustion at low load, and premixed combustion is performed at a partial load up to the rated output after the combustion is stabilized. it reduces the NO _x, also is possible to stabilize the premixed combustion by adopting a variable mechanism for controlling the combustion air flow rate according to the load upon mixing the combination with pre diffusion combustion is disclosed Te. However, this means there is a limit to the low NO _x reduction to adopt easy diffusion combustion NO _x occurs at the time of low load, and is complicated structure of the combustor for variable mechanism for controlling the flow rate of combustion air Therefore, there is a problem that miniaturization is difficult.
[0005]
In order to solve the above-described problems, the applicant of the present application disclosed in Japanese Patent Laid-Open No. Hei 5-296212, provided with an ignition gas outlet at the center, and an outlet hole for the primary mixed gas and the secondary mixed gas around it. A concentric combustion means was proposed. The combustion means performs stable combustion to premixed combustion from ignition, it was possible to achieve low NO _x reduction in the combustion apparatus of a relatively simple structure.
[0006]
However, even with such combustion means, (2) in particular, in a gas turbine combustor that burns fuel gas in air pressurized to a high pressure (eg, 10 at least) by an air compressor, the liner surrounding the combustion chamber is overheated. If the film is cooled by flowing cooling air inward through the liner to cool the liner, the premixed combustion flame in the combustion chamber is cooled by this cooling air, causing the problem of blown out or unstable combustion. was there. Therefore, the combustion under pressure, low NO _x of sufficiently low levels of the present invention to achieve has been extremely difficult. (3) In the combustion means described above, it is necessary to ignite the ignition gas at the center. However, when the conventional fixed or detachable ignition burner is used, the ignition burner itself may be damaged by the flame. However, there is a problem that premixed combustion becomes unstable due to the insertion and removal of the ignition burner. Therefore, in the above-described combustion means, it is difficult to maintain a reliable ignition and stable combustion, and to maintain a low NO _x of the high combustion efficiency from partial load to the rated output be achieved stably It was extremely difficult.
[0007]
The present invention has been developed to solve the above-described problems. That is, the object of the present invention is (1) reliable ignition and stable combustion in pressurized air, and (2) cooling the liner surrounding the combustion chamber without cooling the premixed combustion flame. in that the can, and provides ▲ 3 ▼ moiety high from the time of the load until the maximum output combustion efficiency and low NO _x reduction simultaneously combustor for a gas turbine can be realized.
[0008]
[Means for Solving the Problems]
According to the present invention, an injection of a primary combustion mixed gas having an ignition fuel gas injection hole in the center and a constant mixing ratio of air and fuel gas around the ignition fuel gas injection hole A combustor for a gas turbine in which a hole and a secondary combustion mixed gas injection hole having a variable mixing ratio of air and fuel gas are provided concentrically on the outer periphery of the primary combustion mixed gas injection hole. A cylindrical casing, and a hollow cylindrical liner provided substantially concentrically inside the casing and hermetically partitioning between an inner combustion chamber and an outer combustion air flow path, the liner comprising: Formed with a thin refractory metal and having a diameter-enlarged portion that is expanded to increase the flow rate of the outer air flow, and the outer surface of the expanded portion is formed on a turbulent flow promoting surface that generates turbulence in the air flow The gas turbine is characterized in that the inner surface is formed on a smooth surface with few undulations. Use combustor is provided.
[0009]
According to a preferred embodiment of the present invention, the turbulence promoting surface is formed with a number of turbulence promoting bodies having a surface substantially orthogonal to the air flow. Further, the spark plug further includes a spark plug disposed along the central axis of the casing and having a spark electrode at the tip.
[0010]
According to the above-described configuration of the present invention, the hollow cylindrical liner is provided substantially concentrically inside the hollow cylindrical casing, and the space between the inner combustion chamber and the outer combustion air flow path is airtight. Therefore, the liner heated in the combustion chamber can be cooled with the combustion air, and the combustion efficiency can be increased by preheating the combustion air. Also, unlike conventional film cooling, the cooling air does not flow inward through the liner, so the premixed combustion flame in the combustion chamber burning at a low temperature close to the limit is not cooled, and this flame blows out or becomes unstable. Can be prevented.
[0011]
The liner is made of a thin heat-resistant metal and has a diameter-enlarged portion that is enlarged so as to increase the flow velocity of the outer air flow, and the outer surface of the enlarged-diameter portion generates turbulence in the air flow. Since it is formed on the turbulent flow promoting surface, the air flow whose flow velocity is increased in the expanded diameter part becomes turbulent flow on the turbulent flow promoting surface, and the heat transfer rate is greatly increased. Thus, the liner can be effectively cooled by the combustion air. Furthermore, since the inner surface of the enlarged diameter portion is formed as a smooth surface with few undulations, stable combustion can be maintained without disturbing the premixed combustion flame in the combustion chamber burning at a temperature close to the limit. It is possible to perform lean combustion with thinner fuel gas than before, and it is possible to suppress NO _x emissions while keeping the unburned emissions at low values, which is significantly lower than conventional combustion devices. NO _x conversion can be realized.
[0012]
Further, according to a preferred embodiment of the present invention, since the spark plug having the spark electrode at the tip disposed along the center axis of the casing is provided, a portion that disturbs the flow is not exposed in the combustion chamber, By the spark generated by the spark plug, the premixed gas from the ignition fuel gas ejection hole in the center can be reliably ignited and stable combustion can be performed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each drawing, common parts are denoted by the same reference numerals.
FIG. 1 is an overall configuration diagram (half-sectional view) of a gas turbine including a gas turbine combustor according to the present invention. As shown in this figure, the gas turbine includes an air compressor 1, a turbine 2, a compressor housing 3, a turbine housing 4, a combustor 10 according to the present invention, and the like, and by air pressurized by the air compressor 1, The combustor 10 burns fuel to generate combustion gas, the turbine 2 is driven by the combustion gas, and the air compressor 1 is rotationally driven by the turbine 2.
[0014]
FIG. 2 is a configuration diagram of a gas turbine combustor according to the present invention. The gas turbine combustor 10 of the present invention has an ignition fuel gas injection hole 5 in the center, and a mixture ratio of air and fuel gas is constant around the ignition fuel gas injection hole 5 1. A secondary combustion mixed gas injection hole 6 and a secondary combustion mixed gas injection hole 7 having a variable mixing ratio of air and fuel gas are provided concentrically on the outer periphery of the primary combustion mixed gas injection hole 6. It has been. Such a configuration is similar to a combustion apparatus disclosed in Japanese Unexamined Patent Publication No. 5-296412, this combustion device, performed in the premixed combustion to stabilize the combustion from the ignition, the low NO _x reduction in the combustion apparatus of a relatively simple structure Was able to be realized. The combustor in FIG. 2 is a vertical type in which the axis of the combustor is vertical (vertical), but the present invention is not limited to this, and the horizontal type in which the axis of the combustor is horizontal may be used. There may be.
[0015]
In FIG. 2, the gas turbine combustor 10 of the present invention is further provided with a hollow cylindrical casing 12, a substantially concentric interior inside the casing 12, an inner combustion chamber 11 and an outer combustion air flow path 13. And a hollow cylindrical liner 14 for airtightly partitioning between the two. With this configuration, the liner 14 heated in the combustion chamber 11 can be cooled by the combustion air 13, and the combustion efficiency can be increased by preheating the combustion air 13. Further, unlike the conventional film cooling, the cooling air does not flow inward through the liner, so the premixed combustion flame in the combustion chamber 11 burning at a low temperature close to the limit is not cooled, Unstable combustion can be prevented.
[0016]
Further, in FIG. 2, the liner 14 is formed of a thin heat-resistant metal as a whole. The liner 14 has a diameter-expanded portion 14a that is expanded so as to increase the flow velocity of the outer air flow 8, and the outer surface of the diameter-expanded portion 14a is a turbulent flow promoting surface that generates turbulence in the air flow. The inner surface is formed as a smooth surface with less undulations.
[0017]
FIG. 3 is an enlarged view showing an example of a turbulent flow promoting surface. As shown in this figure, a large number of turbulent flow promoting bodies 15 having a surface substantially orthogonal to the flow of the air flow 8 are formed on the turbulent flow promoting surface. That is, in this figure, the turbulence promoting body 15 is composed of surfaces 15a and 15b that are substantially perpendicular to the air flow 8 and inclined surfaces 15c, and the protrusions that form an acute angle with the air flow 8 by the surfaces 15a and 15c. Is formed. The turbulence promoting body 15 may be formed in a ring shape so as to surround the outer surface of the liner 14 or may be formed by a large number of independent protrusions. Further, the turbulent flow promoting body 15 is not limited to that illustrated in FIG. 3, and may be another known shape.
[0018]
With the liner 14 having the above-described configuration, the air flow 8 whose flow velocity is increased in the enlarged diameter portion 14a becomes a turbulent flow on the turbulent flow promoting surface, and the heat transfer rate is significantly increased. Therefore, heat transfer on the outer surface of the enlarged diameter portion is promoted. The liner 14 can be effectively cooled by the combustion air 8. Furthermore, since the inner surface of the enlarged diameter portion 14a is formed as a smooth surface with less undulations, stable combustion is maintained without disturbing the premixed combustion flame in the combustion chamber 11 that is burning at a temperature close to the limit. can do. Therefore, conventionally above can make thin lean combustion of the fuel gas, NO _x emissions can be suppressed at while suppressing the emission of unburnt to a low value, significant low compared with the conventional combustion apparatus NO _x conversion can be realized.
[0019]
In FIG. 2, a spark plug 16 is disposed along the center axis of the casing 12, and has a spark electrode (not shown) at its tip (lower end in this figure). With this configuration, since the portion that disturbs the flow is not exposed in the combustion chamber 11, the premixed gas from the ignition fuel gas injection hole 5 in the center can be reliably ignited by the spark by the spark plug 16, and stable combustion is achieved. Can be performed.
[0020]
【Example】
FIG. 4 is a diagram showing test results of the gas turbine combustor 10 of the present invention. This figure shows the amount of NO _x in the combustion efficiency and exhaust gas up to the maximum output (output 100%) through the partial load from the output 0%.
[0021]
3 and 4, a premixed gas having a concentration capable of stably igniting is supplied from the ignition fuel gas ejection hole 5, and the premixed gas is ignited by the spark generated by the spark plug 16. Since this ignition is supplied with a relatively rich premixed gas suitable for ignition from the fuel gas injection hole 5 for ignition, ignition can be performed reliably, stable combustion can be performed, and a pilot flame can be formed.
[0022]
Next, a premixed gas having a constant mixing ratio of air and fuel gas is supplied from the jet hole 6 of the mixed gas for primary combustion, and this is burned by the pilot flame P to form a primary flame and output. Increase. The premixed gas for primary combustion is preferably a mixed gas with as little fuel gas as possible within a range where it can be stably burned by the pilot flame. With this operation, as the amount of the primary combustion mixed gas is increased, the output increases and the combustion efficiency increases as shown in FIG. 4, but the NOx amount also increases little by little.
[0023]
Next, after reaching a sufficient load at which secondary combustion can be started, a mixed gas having a smaller fuel gas ratio is supplied from the secondary combustion gas mixture injection hole 7 and burned by the primary flame. To form a secondary flame and increase the output. The secondary flame is preferably subjected to a so-called gas phase oxidation reaction using a thin fuel gas that is close to the limit that can be stably burned. In addition, after forming the secondary flame, it is preferable to reduce the amount of the mixed gas for primary combustion so that the combustion as lean as possible is performed as a whole. As a result of such operation, when the engine load output is 50% or more, the NOx amount after the formation of the secondary flame can be greatly reduced, as shown in FIG. Can do.
[0024]
It should be noted that the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present invention.
[0025]
【The invention's effect】
As described above, the gas turbine combustor according to the present invention can perform reliable ignition and stable combustion in pressurized air, and cools the liner surrounding the combustion chamber without cooling the premixed combustion flame. it can, and can simultaneously achieve high combustion efficiency and low NO _x reduction to the maximum output from the partial load, an excellent effect like.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram (half-sectional view) of a gas turbine including a gas turbine combustor according to the present invention.
FIG. 2 is a configuration diagram of a combustor for a gas turbine according to the present invention.
FIG. 3 is an enlarged view showing an example of a turbulent flow promoting surface.
FIG. 4 is a diagram showing test results of a gas turbine combustor according to the present invention.
FIG. 5 is an overall configuration diagram of a conventional gas turbine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Air compressor 2 Turbine 3 Compressor housing 4 Turbine housing 5 Ignition fuel gas ejection hole 6 Primary combustion mixed gas ejection hole 7 Secondary combustion mixed gas ejection hole 8 Air flow 10 Gas turbine combustor 12 Casing 13 Combustion air flow path 14 Liner 14a Diameter expansion part 15 Turbulence promoting body 16 Spark plug

Claims (3)

There is an ignition fuel gas injection hole in the center, and the primary combustion mixed gas injection hole having a constant mixing ratio of air and fuel gas around the ignition fuel gas injection hole, and the primary In a combustor for a gas turbine, in which a secondary combustion mixed gas injection hole having a variable mixing ratio of air and fuel gas is provided concentrically on the outer periphery of the combustion gas injection hole.
A hollow cylindrical casing, and a hollow cylindrical liner provided substantially concentrically inside the casing and hermetically partitioning between an inner combustion chamber and an outer combustion air flow path, the liner comprising: The outer surface of the expanded portion is a turbulent flow promoting surface that generates turbulent flow in the air flow. A combustor for a gas turbine, wherein the combustor is formed and has an inner surface formed on a smooth surface with little undulation. 2. The gas turbine combustor according to claim 1, wherein the turbulent flow promoting surface is formed with a number of turbulent flow promoting bodies having a surface substantially orthogonal to the air flow. The combustor for a gas turbine according to claim 1, further comprising a spark plug disposed along the central axis of the casing and having a spark electrode at a tip thereof.

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